ABSTRACT
Endokinins designated from the human TAC4 gene consist of endokinin A, endokinin B, endokinin C (EKC) and endokinin D (EKD). EKC/D is a peptide using the common carboxyl-terminal in EKC and EKD and consists of 12 amino acids, and exerts antagonistic effects on the induction of scratching behavior by substance P (SP). Some of SP-preferring receptor antagonists have several d-tryptophan (d-Trp); however, the pharmacological effect of EKC/D-derived peptides with d-Trp remains to be solved. Therefore, to clarify the pharmacological characteristics of EKC/D-derived peptides, effects of pretreatment with these peptides on SP-induced scratching and thermal hyperalgesia, formalin-induced flinching and carrageenan-induced inflammation were evaluated. Intrathecal administration of [d-Trp(8)]-EKC/D and [d-Trp(10)]-EKC/D showed a markedly long inhibitory effect, at least 14 h, whereas the antagonistic effects of [d-Trp(8,10)]-EKC/D and EKC/D without d-Trp disappeared after 1h. Furthermore, the inhibitory effect of [d-Trp(10)]-EKC/D-derived peptides was dependent on the number of amino acids from the amino-terminus, and the more numerous the amino acids, the more marked the antagonistic effect. Thus, these results indicate that the effective duration of EKC/D-derived peptides is dependent on the number of d-Trp in the carboxyl-terminal region and the amino-terminal region regulates the antagonistic effect of EKC/D.
Subject(s)
Analgesics/pharmacology , Anti-Inflammatory Agents/pharmacology , Nociceptive Pain/drug therapy , Peptide Fragments/pharmacology , Posterior Horn Cells/drug effects , Tachykinins/pharmacology , Amino Acid Sequence , Amino Acids/chemistry , Analgesics/administration & dosage , Animals , Anti-Inflammatory Agents/administration & dosage , Behavior, Animal/drug effects , Carrageenan/adverse effects , Formaldehyde/adverse effects , Humans , Hyperalgesia/chemically induced , Immunohistochemistry , Inflammation/chemically induced , Inflammation/therapy , Injections, Subcutaneous , Male , Nociceptive Pain/psychology , Pain Measurement/methods , Peptide Fragments/administration & dosage , Posterior Horn Cells/chemistry , Proto-Oncogene Proteins c-fos/chemistry , Rats , Rats, Sprague-Dawley , Substance P/adverse effects , Substance P/antagonists & inhibitors , Tachykinins/administration & dosage , Time Factors , Tryptophan/pharmacologyABSTRACT
The contribution of tachykinin neurokinin 1 (NK1) receptor to nociceptive processing in the dorsal horn has been evaluated by tachykinin NK1 receptor antagonism and knockout or knockdown of tachykinin NK1 receptor; however, these results have not always been consistent. Therefore, to reevaluate the role of tachykinin NK1 receptor in the dorsal horn, a solution of hemagglutinating virus of the Japan envelope (HVJ-E) with small interfering RNA (siRNA) against tachykinin NK1 receptor was administered intrathecally and then the effect of treatment on tachykinin NK1 receptor immunohistochemistry and on the induction of inflammation, thermal hyperalgesia and scratching behavior was evaluated. This treatment resulted in marked reduction of tachykinin NK1 receptor immunoreactivity through the spinal dorsal horn, and the induction of thermal hyperalgesia and scratching behavior by substance P was significantly attenuated in rats with tachykinin NK1 receptor siRNA. In addition, only one intrathecal injection of tachykinin NK1 receptor siRNA reduced carrageenan-induced inflammation and thermal hyperalgesia significantly and markedly attenuated the induction of flinching after formalin injection and c-Fos expression in the dorsal horn following formalin injection. The efficient down-regulation of tachykinin NK1 receptor by intrathecal administration tachykinin NK1 receptor siRNA suggests that this method may be a valuable tool for examining the function of genes expressed in the dorsal horn.
Subject(s)
Gene Knockdown Techniques , RNA, Small Interfering/administration & dosage , RNA, Small Interfering/genetics , Receptors, Neurokinin-1/deficiency , Receptors, Neurokinin-1/genetics , Animals , Base Sequence , Behavior, Animal/drug effects , Carrageenan/pharmacology , Formaldehyde/pharmacology , Gene Expression Regulation/drug effects , Gene Expression Regulation/genetics , Genetic Vectors/genetics , Hyperalgesia/chemically induced , Hyperalgesia/genetics , Inflammation/chemically induced , Inflammation/genetics , Injections, Spinal , Male , Proto-Oncogene Proteins c-fos/metabolism , Rats , Rats, Sprague-Dawley , Sendai virus/genetics , Spinal Cord/metabolism , Substance P/pharmacologyABSTRACT
Endokinins, encoded by the human preprotachykinin C (PPT-C)/TAC4 gene, are peptides that consist of endokinin A (EKA), B (EKB), C (EKC) and D (EKD) and belong to the tachykinin family. Intrathecal injection of EKC/D (using the common carboxyl-terminal duodecapeptide in EKC and EKD) markedly attenuated the induction of thermal hyperalgesia and scratching behavior by intrathecal administration of substance P (SP), indicating that EKC/D has an antagonistic effect on the neurokinin 1 receptor (NK1R), SP-preferring receptor, at the spinal level; however, the pharmacological function of EKC/D at the periphery is not yet understood. Therefore, to clarify the effect of EKC/D on the peripheral tissue, the effect of subcutaneous injection of EKC/D on carrageenan-induced inflammation was examined. Subcutaneous injection of EKC/D attenuated an increase in paw volume following carrageenan-induced inflammation in a dose-dependent manner. Indeed, the increased paw volume was significantly decreased 40 min after treatment with 10(-4) M (10 nmol) and 10(-3) M (100 nmol) EKC/D (100 microl/rat). Similarly, injection of NK1R antagonists such as L-703,606 and Spantide I (10(-3) M) attenuated the increased paw volume following inflammation. Furthermore, the reduced withdrawal latency evoked by inflammation following subcutaneous injection of carrageenan was also dose-dependently attenuated by EKC/D administration. These results indicate that subcutaneous injection of EKC/D elicits an anti-inflammatory effect on carrageenan-induced inflammation.
Subject(s)
Analgesics, Non-Narcotic/therapeutic use , Inflammation/drug therapy , Neuritis/drug therapy , Peptide Fragments/therapeutic use , Peripheral Nervous System Agents/therapeutic use , Substance P/physiology , Tachykinins/therapeutic use , Analgesics, Non-Narcotic/administration & dosage , Animals , Carrageenan/toxicity , Dose-Response Relationship, Drug , Edema/chemically induced , Edema/drug therapy , Hindlimb , Hot Temperature/adverse effects , Humans , Hyperalgesia/chemically induced , Hyperalgesia/drug therapy , Inflammation/chemically induced , Injections, Subcutaneous , Male , Neuritis/chemically induced , Neurokinin-1 Receptor Antagonists , Peptide Fragments/administration & dosage , Peripheral Nervous System Agents/administration & dosage , Quinuclidines/therapeutic use , Rats , Rats, Sprague-Dawley , Reaction Time/drug effects , Substance P/analogs & derivatives , Substance P/antagonists & inhibitors , Substance P/therapeutic use , Tachykinins/administration & dosageABSTRACT
Two tachykinin peptides, substance P (SP) and hemokinin-1 (HK-1), and three transient receptor potential (TRP) channels, TRPV1, TRPA1 and TRPM8, are similarly localized in the spinal dorsal horn and dorsal root ganglion, suggesting that TRP channels may be related or modulated by these tachykinin peptides. Thus, to clarify whether the responses of TRP channels are modulated by SP or HK-1, the effects of pretreatment with SP or HK-1 on the induction of scratching behavior by TRP channel agonists were examined. Pretreatment with SP or HK-1 enhanced the induction of scratching behavior by resiniferatoxin, a TRPV1 agonist, whereas scratching behavior induced by menthol, a TRPM8 agonist, was suppressed by pretreatment with these peptides. On the other hand, pretreatment with SP, but not HK-1, suppressed the induction of scratching behavior by cinnamaldehyde, a TRPA1 agonist. Taken together, the present results indicate that SP or HK-1 differentially modulated the response of TRPV1, TRPA1 or TRPM8 channel.
